Xerochlamys Baker

Hong-Wa, Cynthia, 2009, Endemic families of Madagascar. XII. Resurrection and taxonomic revision of the genera Mediusella (Cavaco) Hutchinson and Xerochlamys Baker (Sarcolaenaceae), Adansonia (3) 31 (2), pp. 311-339 : 319-320

Genus Xerochlamys Baker

Journal of Botany, British and Foreign 20: 45 (1882). — Leptolaena subgen. Xerochlamys (Baker) Cavaco , Bulletin du Muséum national d’Histoire naturelle, 2e sér., 23: 135 (1951). — Type: Xerochlamys pilosa Baker.

DESCRIPTION

Prostrate subshrubs to shrubs to small trees; young twigs usually flattened, tomentose or sometimes glabrous, older twigs glabrous or pubescent, without white lenticels. Leaves simple, two-ranked, blades entire, without vernation traces, usually pubescent, chartaceous, rarely coriaceous, elliptic, ovate or suboblong, base cordate to rounded, margin entire, plane, occasionally undulate, apex retuse to slightly acute; petiole pubescent, canaliculate; stipules brown, shortly pilose, paired, connate, cone-shaped. Flowers solitary or in inflorescences, terminal or axillary, cymose. Flowers sometimes sessile, often shortly pedicelled, subtended by an involucre; involucre pilose outside, with appressed trichomes inside, fleshy, with 12-28 triangular teeth; sepals green, 3, obovate or sometimes oblong, slightly to deeply emarginate, persistent, imbricate, often abaxially densely pilose, adaxially glabrous, exceeding the involucre; petals 5, obovate or oblong, contorted, glabrous, exceeding the involucre by 7-17 mm; disc annular, toothed; stamens> 20, filament white to greenish, free, slender, of unequal length, anthers yellow, with 2 locules, opening by longitudinal slits; ovary superior, globose to ovoid, with 3 locules, smooth or sulcate, pubescent, style light green, slender, densely pubescent, stigma yellow, 3-lobed. Fruits indehiscent, globose to ovoid, sulcate, exceeding the fleshy involucre; pericarp dissociating into trichome-like structuress at maturity; seeds black to brown, ellipsoid to ovoid, (1-)2-12 per fruit.

KEY TO THE SPECIES OF XEROCHLAMYS BAKER

1. Largest leaf blades ≤ 2 cm wide, elliptic to occasionally ovate ..................................... 2

— Largest leaf blades> 2 cm wide, often ovate to suboblong, sometimes elliptic ............ 5

2. Leaf blades glabrous, rarely with few white trichomes ................................................. 3

— Leaf blades pubescent at least on the abaxial surface ................................................... 4

3. Prostrate shrub; largest leaf blades <2 cm long, glossy green above, green to yellowish beneath; midvein red; petals pink; endemic to Itremo ......................... 7. X. itremoensis

— Erect shrub; largest leaf blades ≥ 2 cm long, dark green above, often whitish beneath; midvein green; petals white, rarely pink; from Ibity to Itremo .................. 6. X. elliptica

4. Leaf blades elliptic to sometimes ovate, margin plane; petiole ≤ 3 mm long; petals pink; from Miarinarivo-Arivonimamo to Isalo ............................................... 3. X. bojeriana

— Leaf blades elliptic, margin undulate, erose (as if bitten by some animal, Stearn 2004); petiole> 3 mm long; petals pale yellow to white; from Isalo to Col des Tapia (Fianarantsoa) ........................................................................................................ 9. X. undulata

5. Leaf blades entirely glabrous, or scarce white trichomes sometimes present ................ 6

— Leaf blades with indumentum on the abaxial surface or at least along the abaxial midvein ................................................................................................................................... 7

6. Leaf blades narrowly ovate to elliptic, coriaceous, base truncate to attenuate, margin irregularly undulate; involucre green, cupulate, brown tomentose; from Andringitra to Mandrare River basin ............................................................................... 4. X. coriacea

— Leaf blades broadly ovate, chartaceous, base cordate to rounded, margin plane; involucre light brown, urceolate, yellow tomentose; from Mt. Vohibasia to Isalo ..... 10. X. villosa

7. Leaf blades elliptic to suboblong, with scattered white indumentum on the abaxial surface or restricted to the abaxial midvein; petals pale yellow; from Cap St André to Tampoketsa d’Ankazobe and Tampoketsa d’Analamaitso ................................... 8. X. tampoketsensis

— Leaf blades ovate to rounded, rarely elliptic, entirely covered with dense golden indumentum at least on the abaxial surface; petals pink; endemic to Itremo .... 5. X. diospyroidea